1. Technical Field
The invention relates in general to semiconductor devices, and more particularly to systems and methods for testing redundant memory elements.
2. Description of the Related Art
A semiconductor device, such as a semiconductor memory device, typically comprises a primary memory array defined by primary rows and primary columns. Illustratively, each row in the primary memory array may represent a word line, and each column in the primary memory array may represent a bit line. The intersection of each row and column may comprise a storage device, such as a dynamic random access memory (DRAM) cell or a magnetoresistive random access memory (MRAM) cell.
During the manufacturing process of the semiconductor device, the primary memory array is tested for defects. If as few as one memory cell is found to be defective, the entire semiconductor device may be considered defective. Thus, to increase yield, the semiconductor device typically includes a redundant memory array defined by redundant rows and redundant columns in the same manner as the primary memory array. Programmable addressing circuitry connected to the primary memory array and the redundant memory array can be programmed to provide redundant rows and redundant columns in the redundant memory array for defective primary rows and primary columns in the primary memory array. The programming of the addressing circuitry is typically accomplished by laser trimming of fuses in a fuse bank.
Because laser trimming the fuses is a permanent process, the redundant memory array is typically tested before selecting a redundant row or redundant column to replace a defective primary row or primary column so as to ensure that a defective redundant row or redundant column is not used to replace the defective primary row or primary column. Test circuitry to support such redundant testing is thus built into the semiconductor device during manufacture. The test circuitry may include a plurality of test pads for receiving test data, and associated test support circuitry, such as addressing circuitry. After the testing and repair process, however, these test pads and support circuitry are typically no longer used.